create dummy for unconnected interface

An interface with no connection is currently omitted from the target
network namespace.  Instead, add a Linux "dummy" interface and assign
IP addresses.

munet/base.py

@@ -2674,6 +2674,34 @@ def add_host(self, name, cls=LinuxNamespace, **kwargs):
 
         return self.hosts[name]
 
+    def add_dummy(self, node1, if1, mtu=None, **intf_constraints):
+        """Add a dummy for an interface with no link."""
+
+        try:
+            name1 = node1.name
+        except AttributeError:
+            if node1 in self.switches:
+                node1 = self.switches[node1]
+            else:
+                node1 = self.hosts[node1]
+            name1 = node1.name
+
+        lname = "{}:{}".format(name1, if1)
+        self.logger.debug("%s: add_dummy %s", self, lname)
+        lhost = self.hosts[name1]
+
+        nsif1 = lhost.get_ns_ifname(if1)
+        lhost.cmd_raises_nsonly(f"ip link add name {nsif1} type dummy")
+
+        if mtu:
+            lhost.cmd_raises_nsonly(f"ip link set {nsif1} mtu {mtu}")
+        lhost.cmd_raises_nsonly(f"ip link set {nsif1} up")
+        lhost.register_interface(if1)
+
+        # Setup interface constraints if provided
+        if intf_constraints:
+            node1.set_intf_constraints(if1, **intf_constraints)
+
     def add_link(self, node1, node2, if1, if2, mtu=None, **intf_constraints):
         """Add a link between switch and node or 2 nodes.
 

munet/native.py

@@ -864,6 +864,31 @@ def get_ifname(self, netname):
                 return c["name"]
         return None
 
+    def set_dummy_addr(self, cconf):
+        if ip := cconf.get("ip"):
+            ipaddr = ipaddress.ip_interface(ip)
+            assert ipaddr.version == 4
+        else:
+            ipaddr = None
+
+        if ip := cconf.get("ipv6"):
+            ip6addr = ipaddress.ip_interface(ip)
+            assert ipaddr.version == 6
+        else:
+            ip6addr = None
+
+        if "physical" in cconf or self.is_vm:
+            return
+
+        ifname = cconf["name"]
+        for ip in (ipaddr, ip6addr):
+            if ip is None:
+                continue
+            self.set_intf_addr(ifname, ip)
+            ipcmd = "ip " if ip.version == 4 else "ip -6 "
+            self.logger.debug("%s: adding %s to unconnected intf %s", self, ip, ifname)
+            self.intf_ip_cmd(ifname, ipcmd + f"addr add {ip} dev {ifname}")
+
     def set_lan_addr(self, switch, cconf):
         if ip := cconf.get("ip"):
             ipaddr = ipaddress.ip_interface(ip)
@@ -2756,8 +2781,9 @@ async def _async_build(self, logger=None):
             if "connections" not in nconf:
                 continue
             for cconf in nconf["connections"]:
-                # Eventually can add support for unconnected intf here.
                 if "to" not in cconf:
+                    # unconnected intf
+                    await self.add_dummy_link(node, cconf)
                     continue
                 to = cconf["to"]
                 if to in self.switches:
@@ -2778,6 +2804,25 @@ def autonumber(self):
     def autonumber(self, value):
         self.topoconf["networks-autonumber"] = bool(value)
 
+    async def add_dummy_link(self, node1, c1=None):
+        c1 = {} if c1 is None else c1
+
+        if "name" not in c1:
+            c1["name"] = node1.get_next_intf_name()
+        if1 = c1["name"]
+
+        do_add_dummy = True
+        if "hostintf" in c1:
+            await n.add_host_intf(c1["hostintf"], c1["name"], mtu=c1.get("mtu"))
+            do_add_dummy = False
+        elif "physical" in c1:
+            await n.add_phy_intf(c1["physical"], c1["name"])
+            do_add_dummy = False
+
+        if do_add_dummy:
+            super().add_dummy(node1, if1, **c1)
+            node1.set_dummy_addr(c1)
+
     async def add_native_link(self, node1, node2, c1=None, c2=None):
         """Add a link between switch and node or 2 nodes."""
         isp2p = False

tests/unconnected/munet.yaml

@@ -0,0 +1,31 @@
+version: 1
+topology:
+  networks-autonumber: true
+  ipv6-enable: true
+  networks:
+    - name: net0
+      mtu: 5000
+  nodes:
+    - name: r1
+      connections:
+        - to: net0
+          name: eth0
+          mtu: 4500
+        - name: unconnected
+          ip: 172.16.0.1/24
+          mtu: 9000
+      cmd: |
+        ip addr show
+        ip -6 addr show
+        which ping
+        tail -f /dev/null
+    - name: r2
+      connections:
+        - to: "net0"
+          name: eth0
+          mtu: 4500
+      cmd: |
+        ip addr show
+        ip -6 addr show
+        which ping
+        tail -f /dev/null

tests/unconnected/test_unconnected.py

@@ -0,0 +1,37 @@
+# -*- coding: utf-8 eval: (blacken-mode 1) -*-
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# June 28 2023, Eric Kinzie <[email protected]>
+#
+# Copyright 2023, LabN Consulting, L.L.C.
+#
+"Testing of unconnected interface."
+import logging
+
+import pytest
+
+# All tests are coroutines
+pytestmark = pytest.mark.asyncio
+
+
+@pytest.mark.parametrize(
+    "unet_perfunc", ["munet", "noinit", "noinit-noshell"], indirect=["unet_perfunc"]
+)
+async def test_unconnected_presence(unet_perfunc):
+    unet = unet_perfunc
+    rc, o, e = await unet.hosts["r1"].async_cmd_status(f"ip addr show dev unconnected")
+    assert rc == 0
+    assert o.find("mtu 9000") > -1
+    assert o.find("inet 172.16.0.1/24") > -1
+
+
+async def test_basic_ping(unet_perfunc):
+    unet = unet_perfunc
+    r1eth0 = unet.hosts["r1"].get_intf_addr("eth0").ip
+    logging.debug("r1eth0 is %s", r1eth0)
+    rc, o, e = await unet.hosts["r2"].async_cmd_status(
+        f"ip ro add 172.16.0.0/24 via {r1eth0}"
+    )
+    assert rc == 0
+    o = await unet.hosts["r2"].async_cmd_raises(f"ping -w1 -c1 172.16.0.1")
+    logging.debug("ping r2 output: %s", o)